#pragma once

#include <iostream>
#include <string>
#include <vector>
#include <fstream>
#include <unordered_map>
#include <mutex>
#include "util.hpp"
#include "Log.hpp"

namespace ns_index
{
    using namespace LogModule;

    struct DocInfo {
        std::string title;      // 文档的标题
        std::string content;    // 文档对应的去标签后的内容
        std::string url;        // 官网文档 url
        uint64_t doc_id;        // 文档的 ID
    };

    struct InvertedElem {
        uint64_t doc_id; 
        std::string word;
        int weight;
    };  

    // 倒排拉链
    typedef std::vector<InvertedElem> InvertedList;
    class Index
    {
    public:
        static Index* GetInstance()
        {
            if(instance == nullptr)
            {
                std::unique_lock<std::mutex> lock(mutex);
                if(nullptr == instance) {
                    instance = new Index();
                }
            }
            return instance;
        }

        // 根据 doc_id 找到文档内容
        DocInfo *GetForwardIndex(const uint64_t doc_id)
        {
            if(doc_id >= _forward_index.size()) {
                std::cerr << "doc_id out range, error!" << std::endl;
                return nullptr;
            }
            return &_forward_index[doc_id];
        }

        // 根据关键字，获得倒排拉链
        InvertedList *GetInvertedList(const std::string &word)
        {
            auto it = _inverted_index.find(word);
            if(it == _inverted_index.end()) {
                LOG(LogLevel::ERROR) << word << " have no InvertedList";
                return nullptr;
            }
            return &(it->second);
        }

        // 根据去标签，格式化之后的文档，构建正排和倒排索引
        // data/raw_html/raw.txt
        bool BuildIndex(const std::string &input)    // parser处理完毕的数据交给我
        {
            std::ifstream in(input, std::ios::in | std::ios::binary);
            if(!in.is_open()) {
                LOG(LogLevel::ERROR) << "sorry, " << input << " open error";
                return false;
            }

            std::string line;
            int cnt = 0;
            while(std::getline(in, line)) {
                DocInfo* doc = BuildForwardIndex(line);
                if(doc == nullptr) {
                    LOG(LogLevel::ERROR) << "build : " << line << " error";     // for debug
                    continue;
                }

                BuildInvertedIndex(*doc);
                cnt++;
                // if(cnt % 50 == 0) 
                LOG(LogLevel::INFO) << "当前已经建立的索引文档: " << cnt;
            }

            in.close();
            return true;
        }

        ~Index()
        {}
    private:
        DocInfo* BuildForwardIndex(const std::string &line)
        {
            // 1. 进行解析line，字符串切分
            // line -> 3 string, title content url
            std::vector<std::string> results;
            const std::string sep = "\3";
            ns_util::StringUtil::Split(line, &results, sep);
            if(results.size() != 3) {
                return nullptr;
            }
            // 2. 字符串进行填充到DocInfo
            DocInfo doc;
            doc.title = results[0];
            doc.content = results[1];
            doc.url = results[2];
            doc.doc_id = _forward_index.size();
            // 3. 插入到正排索引的vector
            _forward_index.push_back(std::move(doc));
            return &_forward_index.back();
        }

        bool BuildInvertedIndex(const DocInfo &doc)
        {
            // title content url doc_id
            // word -> 倒排拉链
            struct word_cnt {
                int title_cnt;
                int content_cnt;

                word_cnt () : title_cnt(0), content_cnt(0) {} 
            };
            std::unordered_map<std::string, word_cnt> word_map;     // 用来暂存词频的映射表

            // 对标题进行分词
            std::vector<std::string> title_words;
            ns_util::JiebaUtil::CutString(doc.title, &title_words);

            // 对标题进行词频统计
            for(auto s : title_words) {
                boost::to_lower(s);     //需要统一转化成为小写
                word_map[s].title_cnt++;
            }

            // 对文档内容进行分词
            std::vector<std::string> content_words;
            ns_util::JiebaUtil::CutString(doc.content, &content_words);

            // 对文档进行词频统计
            for(auto s : content_words) {
                boost::to_lower(s);
                word_map[s].content_cnt++;
            }

#define X 10
#define Y 1
            for(auto &word_pair : word_map) {
                InvertedElem item;
                item.doc_id = doc.doc_id;
                item.word = word_pair.first;
                item.weight = X * word_pair.second.title_cnt + Y * word_pair.second.content_cnt;    // 相关性
                InvertedList &inverted_list = _inverted_index[word_pair.first];
                inverted_list.push_back(std::move(item));
            }

            return true;
        }
    private:
        // 正排索引的数据结构用数组，数组的下标天然是文档的ID
        std::vector<DocInfo> _forward_index; // 正排索引
        // 倒排索引一定是一个关键字和一组 (个) InvertedElem对应[关键字和倒排拉链的映射关系
        std::unordered_map<std::string, InvertedList> _inverted_index;
    private:
        Index() {}
        Index(const Index&) = delete;
        Index& operator=(const Index&) = delete;

        static Index* instance;
        static std::mutex mutex;
    };

    Index* Index::instance = nullptr;
    std::mutex Index::mutex;
}